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Molecular Alterations in Spontaneous Sputum of Cancer-Free Heavy Smokers: Results from a Large Screening Program

Authors' Affiliations: ¹ Molecular Genetics Laboratory, Departments of ² Thoracic Surgery, ³ Oncology, ⁴ Radiology and Imaging Diagnostics, and ⁵ Pathology, IRCCS Istituto Clinico Humanitas; ⁶ Consultant Statistician, Lega Italiana per la Lotta contro i Tumori, Milan, Italy; and ⁷ Department of Thoracic Surgery, Istituto Clinico Humanitas Gavazzeni, Bergamo, Italy

Requests for reprints: Massimo Roncalli, Department of Pathology, University of Milan, IRCCS Istituto Clinico Humanitas, Via Manzoni 56, 20089 Rozzano, Milan, Italy. Phone: 39-02-82244714; Fax: 39-02-82244791; E-mail: massimo.roncalli{at}unimi.it.

Purpose: The high mortality rate for lung cancer is likely to be reduced by the development of a panel of sensitive biological markers able to identify early-stage lung cancers or subjects at high risk. The aim of this study was to establish the frequency of K-ras and p53 mutations and p16^INK4A, RASSF1A, and NORE1A hypermethylation in sputum of a large cohort of cancer-free heavy smokers and to assess whether these markers are suitable for a routine use in the clinical practice for the early diagnosis of pulmonary cancer.

Experimental Design: Sputum samples were collected from 820 heavy smokers. Inclusion criteria consisted of radiologic and cytologic absence of pulmonary lesions, age at least 60 years, male gender, and a smoking history of at least 20 pack-years.

Results: The analysis identified 56 individuals (6.9%) with one molecular alteration. p53 mutation and p16^INK4A, RASSF1A, and NORE1A methylation frequencies were 1.9%, 5.1%, 0.8%, and 1.0%, respectively; no K-ras mutations were found. One patient with p53 mutations was diagnosed with an early-stage lung cancer after 3-years of follow-up. The molecular analysis of bronchoscopy samples confirmed in half of the cases alterations present in sputum without revealing additional molecular changes.

Conclusions: Genetic and epigenetic abnormalities can be detected in cancer-free heavy smokers. Although the predictive value of the cancer risk is still to be established as it requires not less than 5 years of follow-up, p53 and p16^INK4A are more promising candidates than K-ras, RASSF1A, and NORE1A for the pulmonary molecular screening of heavy smokers healthy individuals.